Optimal Methodology for the Quantification of Binding Constants from Spectrophotometric Titration Data

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Speaker: Prof. Douglas A. Vander Griend, Ph.D. Calvin University Grand Rapids, Michigan, USA.

Abstract:
Spectrophotometric titration data can be modeled to simultaneously determine 1) the number of distinct chemical species formed over the course of the experiment, 2) the stoichiometry of each species, 3) the spectroscopic signature of each species, and 4) the equilibrium constants for the associative chemical reactions between the species. The precise values of these binding constants are especially valuable for thermodynamically characterizing ensembles of molecules in solution. Any spectroscopic signal that scales directly with concentration can be used. Experiments should be designed to optimize the sensitivity of the binding constants to the data. Multiple equilibrium constants can be ascertained without prior knowledge of the species that form. Negative numbers must be handled astutely. Uncertainty ranges for the binding constants, which are inherently asymmetric, can be properly quantified via bootstrapping by chemical solution on the original dataset. Finally, a hybrid particle swarm optimization technique has been used to simultaneously optimize both the stoichiometry ratios and binding constants thereby automating the search potential chemical species.

Several example systems that will be featured include the self-assembly of a [Cu4L4]4+ supramolecular square, the stepwise coordination of nickel(II) with amines, and the binding of anions to a macrocyclic polyamide cage.

Biography:
Prof. Dr. Douglas Vander Griend is professor of Chemistry and director of the Clean Water Institute at Calvin University in Grand Rapids, Michigan. After winning the Dreyfus Postdoctoral fellowship in 2000 at the Furman University in South Carolina, he specialized in nanomolecular building projects (Tinker Toys) and development of nanostructures. Modelling of such system is performed using advanced math and computer code applied to spectroscopic measurements. He currently has 6 patents and over 40 publications on thermochromic windows (i.e. systems that change color according to temperature), solid state arrangements and supramolecular assembly.

Host: Prof. Vittorio Limongelli